The present invention relates to a thin-film laminate that may be applied to organic electronic devices such as organic electroluminescence (EL) elements, organic photoelectric conversion elements, and organic transistors, an organic transistor using the same, and the like.
Organic electronic technology that enables an increase in area and a reduction in thickness and weight and ensures flexibility when using a flexible substrate, has attracted attention.
An organic transistor is used as a switching device. A low-molecular-weight organic material such as pentacene has been studied.
It has not been reported that a transistor using a low-molecular-weight organic material exhibits a high mobility of about 1 cm2/Vs in an amorphous state. Moreover, since a single crystal cannot be formed, an increase in mobility has been attempted by controlling a polycrystalline state.
A study on a pentacene transistor conducted by the Pennsylvania university since 1997 achieved a remarkable progress with regard to an increase in mobility (Y.-Y. Lin, D. J. Gundlach, S. F. Nelson and T. N. Jackson: IEEE Trans. Electron Devices, 44 (8), 1325 (1997)).
For example, a mobility 1.5 cm2/Vs, an ON/OFF ratio of 108, and a sub-threshold slope of 0.5 V/decade have been reported.
Pentacene is a polyacene compound that has a pi-conjugated molecular structure. Pentacene exhibits a high mobility due to pi electrons, and shows semiconductor properties.
However, it is difficult to crystallize pentacene due to its planar molecular structure. When forming a film having a thickness of several hundreds of angstroms, dendritic pentacene is generally grown over several micrometers to produce a structure in which the molecules are finely stepped. Therefore, it is difficult to obtain a film having a stable superlattice structure.
When forming a thick film using a pentacene organic semiconductor or the like, the initial two-dimensional growth changes into three-dimensional growth so that it is difficult to form a continuous semiconductor layer on the upper side.
An object of several aspects of the invention is to provide a thin-film laminate that allows a film structure that generally becomes a dendritic structure or the like by known semiconductor layer deposition and does not exhibit uniformity to form a flat film by forming a stacked structure of a first organic layer that is controlled at a molecular layer thickness level and a second organic layer differing from the first organic layer or an ultrathin inorganic insulating layer.